Hot weather hard start.
06-21-2008, 04:21 PM
#1
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Hot weather hard start.
My car takes about 3-5 seconds to start when the weather is hot (80+). The hotter it is the harder it is to start. When it does start it blows a little smoke out the tailpipe for a second. I would naturally think G62 coolant temp sensor but it is new and tests fine per bentley. Also, it seems to run better/smoother and have more power before it is fully warm. The crank position sensor has about 7k miles on it so I doubt it is that. I have no CEL or faults. FPR is new but may be slightly out of adjustment (i am trying to get it dialed in right now).
06-21-2008, 04:56 PM
#2
G62 wouldn't stop the engine from starting, just make it run rich. Your suspects have to be...
1. Cam position sensor. When they first start to go, they don't like warm temps (Cooling it down with water poured down the back of the cam sprocket has been know to help.
2. Fuel Pump - check valve may be wonky and allowing the fuel to drain out of the system, back to the fuel tank.
3. Fuel Pressure regulator maybe leaking, allowing fuel to drain out of the fuel rail while the engine is off. Needs a few seconds under cranking to fill and pressurize the fuel rail.
4. Something else.
2. Fuel Pump - check valve may be wonky and allowing the fuel to drain out of the system, back to the fuel tank.
3. Fuel Pressure regulator maybe leaking, allowing fuel to drain out of the fuel rail while the engine is off. Needs a few seconds under cranking to fill and pressurize the fuel rail.
4. Something else.
06-21-2008, 05:32 PM
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Dave, would you say that I can rule the cam sensor out because
If the car hasn't been run yet (motor is cold) but the ambient outside temp is 90 it is hard to start.
However, if the car has been running, the motor is hot and it is cooler out (60) it starts right up. Under the same scenario but when the outside temp is 90 it will not start right up.
I would think the heat around the CPK from the motor would be much hotter after running than the outside temp when the motor is cold and therefore I can rule that sensor out. Make sense or am I making an assumption that is incorrect?
However, if the car has been running, the motor is hot and it is cooler out (60) it starts right up. Under the same scenario but when the outside temp is 90 it will not start right up.
I would think the heat around the CPK from the motor would be much hotter after running than the outside temp when the motor is cold and therefore I can rule that sensor out. Make sense or am I making an assumption that is incorrect?
06-21-2008, 06:08 PM
#4
CPK? Otherwise, I *think* you made sense. The common thread is ambient air temp according to your
<center><img src="http://pictureposter.audiworld.com/61424/ecuinputfigure.jpg"></center><p>
"data".
Based on the input list in the diagram, the only thing that seems to fit is the G42 Intake Air Temp (IAT) sensor. Follow the link for more info.<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/148740.phtml">Click here for more info, including a link to a IAT test procedure</a></li></ul>
"data".
Based on the input list in the diagram, the only thing that seems to fit is the G42 Intake Air Temp (IAT) sensor. Follow the link for more info.<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/148740.phtml">Click here for more info, including a link to a IAT test procedure</a></li></ul>
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